A tracked vehicle has a track extending around a series of track guide wheels. At least some of the guide wheels support the weight of the vehicle hull on the section of the track which is in contact with the ground. In this specification, the expression “hull” is used to refer to the main body of the vehicle. The hull serves the same purpose as the chassis of a conventional vehicle, whether or not the chassis is constituted wholly or partially by the bodywork of the vehicle. Consequently, the context of the present invention, the word “hull” is considered to be equivalent to a vehicle chassis.
The track guide wheels which support the weight of the vehicle on the ground need to be connected to the vehicle hull by a suspension arrangement which enables the track guide wheel to move upwardly and downwardly relatively to the hull.
A suspension system is known in which the suspension system comprises an arm which is pivotable relatively to the hull about a pivot axis. A wheel-supporting shaft is carried by the arm at a position away from the pivot axis, for supporting a track guide wheel. A resilient damping arrangement is accommodated within the arm for providing damped resilient resistance to deflection of the arm away from a static position in a direction corresponding to movement of the hull towards the ground.
In the known unit, the arm is supported for pivotal movement on a hub which is secured directly to the vehicle hull. For this purpose, the hull is formed with an array of tapped holes for receiving fasteners, in the form of bolts, which pass through a corresponding array of holes in a flange of the hub into the tapped holes in the vehicle hull.
A problem with such suspension units is that they cannot easily be retrofitted to a vehicle in substitution for a suspension unit of a different type. This is because the holes in the vehicle hull for securing the previous suspension unit will almost certainly not coincide with the array of holes in the hub flange. Consequently, at best, new holes need to be formed in the vehicle hull to coincide with the holes in the hub flange. Even this may be difficult if, for example, one or more of the new holes coincides approximately, but not completely, with one or more of the original holes. In any case, the extra holes in the vehicle hull can weaken it, which is undesirable at the location of the hull at which the suspension unit is fitted, and particularly undesirable in a military vehicle.